Hi all,

I see that everyone is nervous about the new Binos from Baader and how the
diopter adjustment works, and whether the eyepieces rotate or not.

In my opinion, whether the eyepieces rotate or not is a non-issue. I have
tested just about every eyepiece that I would use in a Binoviewer, rotated them
by hand and found them to be well centered, well enough that I saw no image
shift. Nevertheless, if you do have some ultra-cheap eyepieces that are not
centered, or very short focus eyepieces (more on that below), you will run into
other issues anyhow. One of them is, how will you know which way the eyepiece is
rotated to begin with whenever you insert them into the bino at night when you
can't see which way they are facing? Second question is, are you always sure
to insert eyepiece A into the left channel and eyepiece B into the right
channel? This makes a difference if they are cheap, off center and have slightly
different focal lengths.

The way Baader designed the new eyecups, he tried to get the lowest profile
eyecups so that you don't run into the problem of not enough back focus. These
new eyecups achieve the goal of diopter adjustment and positive locking while
keeping the eyepiece exactly centered with no more eyecup height than before.
Do the eyepieces rotate when you turn the diopter? That depends how you do it.
The eyepieces sit inside a non-rotating sleeve, and if you turn the upper
diopter adjusting barrel, while keeping slight tension on the click-lock
mechanism with your other thumb, the eyepiece will slowly move outward without
rotating. Is this really necessary? Not in my opinion. If you don't hold the
bottom
part with your thumb, the eyepiece might or might not turn a bit, depending how
loose it sits in its barrel.

The eyepiece holders are not easily removed and have been precisely
collimated at the factory. It is not recommended that you take them apart to
replace
them with other barrels, or try to collimate them yourself. It would take some
heavy hammer blows to change the collimation, so please no hammers.

The coatings are new and have been optimized for visual, because this is
after all a strictly visual device. As such, the coatings have a null in the
yellow-green to give the highest possible transmission. The beam splitter uses a
dielectric coating which is also more efficient, but does introduce some
polarization. This is not an issue for any night use, but may make one image a
tad
brighter than the other under certain daytime lighting conditions where the
light is polarized. I have looked through them in the daytime and found no
effect
that I could see myself. They look just like my original Zeiss versions.

Recommended eyepieces. I have no particular eyepiece recommendations as to
type, except to say that the longer focal length eyepieces are going to give you
the best view. To explain a bit further, if you want high power, it is better
to produce this before the prism set than afterwards. The rewards are many,
including longer eyerelief, less sensitivity to tiny miscollimations and much
lower amounts of optical aberrations due to the long prism path itself. If you
have a fast scope, F7, F6, F5 or even shorter, it makes no sense to use 5mm,
4mm or 3mm eyepieces to get up to planetary powers. You will magnify not only
all the prism aberrations, but also any image offsets that might be in the
eyepiece barrels or the prisms themselves. You may have trouble merging the
image.
Even if you could adjust the collimation precisely by moving the eyecups
around, the next time you insert the eyepieces, they won't be in the exact same
orientation and all your collimation efforts will be for naught.

My rule of thumb for any Binoviewer is to use focal lengths no shorter than
10mm, preferably 12mm for high power viewing. Insert a Barlow element ahead of
the Bino to achieve a long focal length. This will narrow the beam
considerably over prime focus, with the result that the active area for each
object beam
will occupy only a tiny portion of the prism faces. This will really cut down
on aberrations in the optical path. This applies to every Binoviewer out
there. While the Baader prism are top notch, and better in my opinion than any
others, they are not perfect. They will, however produce a perfect Airy disc
when
used with a Barlow ahead of the optical path. If you are looking for that last
2% for those subtle Mars features, think long eyepice, long F-ratio, and you
will dazzle them.

Roland Christen